Flight planning represents complex task for air carriers where many of analysis are needed, so flight can be economically payable, and at the same time available to the passengers. This disertation presents all the aspects which need to be taken into consideration while planning a flight, and they include routes, operative procedures, staff regulations. Further more, the procedure of flight planning is defined and detailed descripted, belonging flight plan formats, their contents and changes. Listed data are being analized on the basis of ICAO Annexes and miscellaneous documents. After the submitted flight plans to the Network Management Operations Centre, flight plan messages are being processed to all services concerned in a flight plan. Types of messages are being elaborated with their meanings, processing and abbreviations. Also, prior to accepted flight plan, flow of all required actions is being shown.